In key telephone systems the line control boards have handles positioned along the edge opposite the terminals for the purpose of providing gripping surfaces for removing the printed wiring boards from the network. Typically, the handles are provided with apertures containing electrical terminals which can be interconnected in various combinations to provide different operational or test characteristics for the associated line circuit.
The -48 volt line test function on an existing type of line circuit currently requires the craftsperson to insert the blade of a small screwdriver into an aperture of the handle to provide a short between two test terminals. Such a testing arrangement has the drawback that a possible shock hazard may exist if the test is performed by an unskilled person.
Thus, it is desired to design a test arrangement which would eliminate any possible shock hazard when the test function is performed by an unskilled person. Moreover, it is desired that any circuit additions or modifications required to implement the test function be minimized and economically adaptable to existing key telephone line circuits.